Vehicle ignition systems provide spark to engine cylinders in a controlled manner. Conventional vehicle ignition systems for internal combustion engines include spark plugs, a high voltage coil and a distributor which directs high voltage power through spark plug wires to the spark plugs. Recently, distributorless systems which rely upon microprocessor control have been introduced to more precisely control engine operation. In such systems, the distributor is eliminated and a microprocessor controls engine operation based upon data generated as a result of engine operation. Systems which utilize a distributor only require a single coil for four, six or eight cylinders in standard engine configurations. With a distributorless ignition system, one coil is generally used to develop a high voltage output for one or two spark plugs.
When servicing conventional ignition systems, it is necessary to analyze each of the components as well as each of the spark plug wires to determine which part or parts of the system require repair or replacement. This can be quite time consuming and requires skilled mechanics to perform the repair. Recently, modular groups of ignition parts have been proposed to connect an ignition coil or coils to several spark plugs simultaneously. Using a single unit to house the components of an ignition system provides advantages when servicing the ignition system. A mass produced part can be quickly removed and replaced. The replacement part can be fully checked for purposes of quality control resulting in improved reliability and customer service.
Providing a sealed spark distribution cassette including the coil improves durability. Housing the components in a single unit also protects the individual components from deterioration due to moisture or operation under harsh conditions.
The use of a single coil to provide four high voltage outputs for four separate cylinders is disclosed in U.S. Pat. No. 4,392,473 to Tsutsui et al. The Tsutsui patent discloses an ignition unit having high voltage terminals, high voltage diodes and ignition coils which are assembled together and potted in a synthetic resin. Spark plug wires are used to connect the output of the coil to the spark plugs. Lead wires are also used to connect the high voltage diodes associated with the coil taps to the spark plug wire terminals. The assembly of the Tsutsui ignition unit is complicated in that many connections to the diodes and coil must be soldered or otherwise connected together. The complex installation process required by the Tsutsui patent results in a system wherein significant costs are incurred for ignition part service.
A Cassette-type ignition system is disclosed in U.S. Pat. No. 4,706,683 to Johansson et al which is designed to be mounted directly over the spark plugs of an internal combustion engine. The Johansson patent discloses a system wherein circuit boards are imbedded in the unit with epoxy and the ignition components of the system are included on the circuit boards. A single coil is provided for each engine cylinder. A capacitive discharge circuit is used to store charge and provide current to the spark plug. The use of circuit boards in the cassette assembly and capacitive discharge circuits result in increased cost of the cassette assembly due to increased manufacturing and component cost. Many soldered connections are required to complete the assembly of the Johansson unit.
Another example of a modular ignition system is disclosed in U.S. Pat. No. 4,706,639 to Boyer et al wherein the ignition module is mounted directly over the spark plugs of an internal combustion engine. The module disclosed in Boyer utilizes one coil for every two cylinders. Wires are used to connect the terminals to the ignition coil which necessitates soldering connections in the ignition module.
The present invention is directed to solving the problems confronted by the prior art ignition systems and processes for making modular ignition system components described above.